High pressure sparking device



April 26, 1966 H. A. KERSHNER 3,247,76

HIGH PRESSURE SPARKING DEVICE Filed March 23. 1964 g3 if INVENTOR.HOWARD IEKIRSHNER .;/S m. M k

fl la? M i9 l fi ATTORNEYS:

United States Patent 3,247,796 HIGH PRESSURE SPARKING DEVICE Howard A.Kirshner, Levittown, Pa., assignor to the United States of America asrepresented by the Secretary of the Army Filed Mar. 23, 1964, Ser. No.354,181

.10 Claims. (Cl. 102-46) The invention described herein may bemanufactured and used by or for the Government for governmental purposeswithout the payment to me of any royalty thereon.

This invention relates to a high pressure sparking device andparticularly, to a spark igniter capable of withstanding high pressuresgenerated by ignition of fuel or propellant.

In the past electric firing circuits for small arms and other roundshave utilized conductive primer mixes for initiating propellant. Use ofconductive mix primers is attended by the disadvantage of non-isochronicignition of the propellant bed, thereby limiting the degree of ballisticcontrol available from a given propellant grain design. Isochronicignition can be achieved if the propellant bed is surrounded by acombustible vapor which is spark ignited. Spark ignition by means ofconventional spark plugs was precluded by their inherent inability towithstand the high pressures generated by the subsequent burning of thepropellant charge. Further performance of conventional spark plugs isdependent upon the dielectric properties of the medium between theelectrodes, said dielectric properties varying with temperature andother conditions.

Accordingly, a principal object of the present invention is to provide adevice for producing a spark in a chamber where high pressure will beencountered unattended by the foregoing disadvantages of the prior art.

Another object of the invention is to provide a high pressure sparkingdevice for use in an electric firing circuit.

A further object of the invention is to provide an improved roundemploying an electric sparking device.

Other objects of the invention will in part be obvious and in partappear hereinafter in the following disclosure FIG. 1 depicts across-sectional view of one embodiment of the inventive highpressure-sparking device, and

FIG. 2 depicts an electric firing circuit for the inventive device.

The invention may be best understood by consideration of an ordinaryelectric primer cup. Such a cup has an insulated ring separating theouter cup from a centered electrode, which may take the form of a buttonor rivet. According to the present invention this insulated ring iscoated on the inside of the cup by an electrically conductive material,such as graphite, thereby enabling the primer component to function as aspark plug. Using an electric firing circuit such as is normally usedwith electric primers, the modified primer component can produce a sparkor flash. Since the primer component is designed to fit into a cartridgecaseand since the assembled round withstands gun pressures in normalfirings, the inventive sparking device is capable of withstanding thehigh pressures encountered in electrical firing.

In the course of the investigation leading to the present invention, anordinary unloaded electric primer was employed and the insulated ringwas coated on the inside of the cup with ordinary pencil lead. Themodified device was inserted into the base of a caliber .60 cartridgeloaded with solid propellant and a combustible vapor. Closing of thecircuit resulted in a successful firing. The caliber .60 cartridge wasconventional in structure with the ex- ICC ception of the primer cup andincluded a cartridge case having a tubular body with abase at one endand a neckeddown portion at the other end. The base defined a primer cuppocket centrally therein for press-fitting of the modified primer cupwith its open end inward. A projectile was press-fitted within thenecked-down portion and extended outwardly. The term solid propellant isherein defined to include solid compositions containing sufficientoxygen within their structure to effect their transformation intogaseous products and which undergo a series of chemical processes, whensubjected to a suitable ignition stimulus, to effect conversion intosuch gaseous products without the addition of oxygen from an externalsource. Illustrative of typical solid propellants contemplated are thoserecited in Solid Propellant Rockets by Clayton Huggett et al., PrincetonUniversity Press, Princeton, NJ. (1960) at page 4. The term combustiblevapor is herein defined to include combustible gas. Illustrative oftypical combustible gases contemplated are those recited in Websters NewInternational Dictionary of the English Language, Second EditionUnabridged, G.&C. Merriam Company, Springfield, Mass. (1953) at page1036.

The invention may be more fully understood by recourse to the drawings.In FIG. 1 primer cup 2 is separated from center electrode 3 by aninsulation ring 4. A

-ring of graphite 5 acts as a carbon bridge between electrode 3 and theinside of primer cup 2. Since this in effect, permits the device of FIG.1 to behave like a semiconductor type plug, operation of the device isrelatively independent of the environment.

FIG. 2 shows a diagram of the electric firing circuit wherein theinvention is employed. A battery 10 or other electric power sourcecreates a potential difference between the plates of capacitor 11.Capacitor 11 is designed to accumulate a suflicient charge to cause theinventive high pressure sparking device 12 to spark when the circuitbetween capacitor 11' and device 12 is closed, as by throwing switch 13.

It will be further understood that various other changes may be made inthe inventive device and the use thereof without departing from thespirit and scope of this invention. For example, the invention may beemployed to initiate spark-sensitive liquid propellants. The term liquidpropellants is herein definedv to include any liquid chemical which isan essential component of the chemical skilled in the art may be able tounderstand and prac-' tice the same, I state that what I desire tosecure by Letters Patent is defined in what is claimed.

I claim: 1. In an electric firing system comprising a high pressuresparking device, means for storing electrical energy up to the sparkingvoltage of said device, means for supplying electrical energy to saidstorage means, and selector switch means connected between said deviceand said storage and supply means for closing a first circuit betweensaid storage and supply means to permit storing of.electri cal energy upto the sparking voltage of said device and alternatively for closing asecond circuit between said storage means and said device to permitdischarge of stored electrical energy to effect sparking of said device,

the improvement wherein said device comprises a primar cup having ahollow, cylindrical body separated by insulation means from an electrodeforming a closure at one end thereof, the other end of said body beingopen,

a cartridge case having a tubular body with a base at one end and anecked-down portion at the other end, said base defining a primer cuppocket centrally therein,

said primer cup being press-fitted within said pocket with its open endinward,

a projectile press-fitted within said necked-down portion and extendingtherefrom, and

solid propellant granules bathed in combustible vapor filling the voidenclosed by said case, said void being free from any primingcomposition.

2. An electric firing system according to claim 1 wherein said primercup body and electrode are linked by a Weakly conductive bridge ofgraphite particles within said cup.

3. In an electric firing system comprising a high pressure sparkingdevice,

means for storing electrical energy up to the sparking voltage of saiddevice,

means for supplying electrical energy to said storage means, and

selector switch means connected between said device and said storage andsupply means for closing a first circuit between said storage and supplymeans to permit storing of electrical energy up to the sparking voltageof said device and alternatively for closing a second circuit betweensaid storage means and said device to permit discharge of storedelectrical energy to effect sparking of said device,

the improvement wherein said device comprises a primer cup having ahollow, cylindrical body separated by insulation means from an'electrodeforming a closure at one end thereof, the other end of said body beingopen,

a cartridge case having a tubular body with a base at one end and anecked-down portion at the other end, said base defining a primer cuppocket centrally therein,

said primer cup being press-fitted within said pocket with its open endinward,

a projectile press-fitted within said necked-down portion and extendingtherefrom, and

spark-sensitive liquid propellant filling the void enclosed by saidcase, said void being free from any priming composition.

4. An electric firing system according to claim 3 wherein said primercup body and electrode are linked by a weakly conductive bridge ofgraphite particles within said case.

5. A cartridge for use in an electric firing system comprising a primarcup having a hollow, cylindrical body separated by insulation means froman electrode forming a closure at one end thereof, the other end of saidbody being open,

a cartridge case having a tubular body with a base at one end and anecked-down portion at the other end, said base defining a primer cuppocket centrally therein,

said primer cup being press-fitted within said pocket with its open endinward,

a projectile press-fitted within said necked-down portion and extendingtherefrom, and

solid propellant granules bathed in combustible vapor filling the voidenclosed by said case, said void being free from any primingcomposition.

6. A cartridge according to claim 5 wherein said primer cup body andelectrode are linked by a weakly conductive bridge of graphite particleswithin said case.

7. A cartridge for use in an electric firing system com- 5 prising aprimer cup having a hollow, cylindrical body separated by insulationmeans from an electrode forming a closure at one end thereof, the otherend of said body being open, cartridge case having a tubular body with abase at one end and a necked-down portion at the other end, said basedefining at primer cup pocket centrally therein,

said primer cup being press-fitted within said pocket with its open endinward,

a projectile press-fitted within said necked-down portion and extendingtherefrom, and

spark-sensitive liquid propellant filling the void enclosed by saidcase, said void being free from any priming composition.

3. A cartridge according to claim 7 wherein said primer cup body andelectrode are linked by a weakly conductive bridge of graphite particlesWithin said case.

9. In an electric firing system comprising a high pressure sparkingdevice,

means for storing electrical energy up to the sparking voltage of saiddevice,

means for supplying electrical energy to said storage means, and

selector switch means connected between said device and said storage andsupply means for closing a first circuit between said storage and supplymeans to permit storing of electrical energy up to the sparking voltageof said device and alternatively for closing a second circuit betweensaid storage means and said device to permit discharge of storedelectrical energy to eifect sparking of said device,

the improvement wherein said device comprises a primer cup having ahollow, cylindrical body separated by insulation means from an electrodeforming a closure at one end thereof, the other end of said body beingopen,

a cartridge case having a tubular body with a base at one end and anecked-down portion at the other end, said base defining a primer cuppocket centrally therein,

said primer cup being press-fitted within said pocket with its open endinward,

a projectile press-fitted within said necked-down portion and extendingtherefrom, and

a spark-sensitive propellant within the void enclosed by said case, saidvoid being free from any priming composition.

10. A cartridge according to claim 9 wherein said primer cup body andelectrode are linked by a weakly conductive bridge of graphite particleswithin said case.

References Cited by the Examiner UNITED STATES PATENTS 39,542 8/1863Beardslee 102-28 319,628 6/1885 Russell 102-46 1,229,049 6/1917Dissinger 102 38 1,704,302 3/1929 Ruhlemann 10270.2 2,918,871 12/1959Taylor 102-46 X 2,960,032 11/1960 Sahlin 102-46 OTHER REFERENCESInternal Ballistics of Solid-Fuel Rockets, first edition, 0 McGraw-HillBook Company, Inc., 1950, page 4 (required).

BENJAMIN A. BORCHELT, Primary Examiner. R. F. STAHL, Assistant Examiner.

1. IN AN ELECTRIC FIRING SYSTEM COMPRISING A HIGH PRESSURE SPARKINGDEVICE, MEANS FOR STORING ELECTRICAL ENERGY UP TO THE SPARKING VOLTAGEOF SAID DEVICE, MEANS FOR SUPPLYING ELECTRICAL ENERGY TO SAID STORAGEMEANS, AND SELECTOR SWITCH MEANS CONNECTED BETWEEN SAID DEVICE AND SAIDSTORAGE AND SUPPLY MEANS FOR CLOSING A FIRST CIRCUIT BETWEEN SAIDSTORAGE AND SUPPLY MEANS TO PERMIT STORING OF ELECTRICAL ENERGY UP TOTHE SPARKING VOLTAGE OF SAID DEVICE AND ALTERNATIVELY FOR CLOSING ASECOND CIRCUIT BETWEEN SAID STORAGE MEANS AND SAID DEVICE TO PERMITDISCHARGE OF STORED ELECTRICAL ENERGY TO EFFECT SPARKING OF SAID DEVICE,THE IMPROVEMENT WHEREIN SAID DEVICE COMPRISES.